Catalysts are used in many chemical reactions. One such chemical reaction is the polymerization of olefines, wherein catalysts are fed, e.g., into a polymerization reactor as a suspension in some hydrocarbon medium. In such process, the catalyst mixture is usually fed from a separate feeding container as a mud-like catalyst suspension by means of a feeding or batching device into the polymerization reactor. Since polymerization processes are often continuous, it must be possible to continuously batch an exactly desired amount of the catalyst into the polymerization reactor. Since catalysts are often relatively thick mud-like mixtures, it sets high requirements for the operation and operational reliability of the batching device.
Such a catalyst feeding system has previously been described e.g. in U.S. Pat. No. 3,227,312. Therein is described a feeding device comprising a rotatable plug valve having two through channels which do not communicate with each other. As the plug rotates, each channel is alternately in contact with the catalyst feeding container, whereby it is filled with the catalyst mixture. As the plug further rotates, the channel filled with the catalyst comes into a position in which it communicates both with the polymerization reactor and a transfer medium block, and the medium coming from the block transports the catalyst from an inlet channel into the polymerization reactor. At the same time, another inlet channel has in turn rotated in such a way that it communicates with the catalyst feeding container and is thus filled with the catalyst mixture.
According to the operating principle of the feeding device of such a position that it communicates with the catalyst feeding container, it is simultaneously filled with pure transfer medium. This is also a disadvantage, since it further makes the flowing of the mud-like catalyst mixture into the inlet channel more difficult. As a consequence, the filling of the inlet channels slows down or the inlet channels are filled only partially, and furthermore, the feeding capacity of the feeding device decreases, and at the same time, the production rate of the polymerization process decreases.